Navigation systems assist users in locating objects. For instance, navigation systems are used in industrial, aerospace, and medical applications. In the medical field, navigation systems assist surgeons in placing surgical tools relative to a patient's anatomy. Surgeries in which navigation systems are used include neurosurgery and orthopedic surgery. Typically, the tool and the anatomy are tracked together with their relative movement shown on a display.
Navigation systems may employ light signals, sound waves, magnetic fields, radio frequency signals, etc. in order to track the position and/or orientation of objects. Often the navigation system includes tracking devices attached to the object being tracked. A localizer cooperates with tracking elements on the tracking devices to determine a position of the tracking devices, and ultimately to determine a position and/or orientation of the object. The navigation system monitors movement of the objects via the tracking devices.
Many navigation systems rely on an unobstructed line-of-sight between the tracking elements and sensors of the localizer that receive tracking signals from the tracking elements. These navigation systems also rely on the tracking elements being positioned within a field-of-view of the localizer. As a result, efforts have been undertaken to reduce the likelihood of obstructing the line-of-sight between the tracking elements and the sensors and to maintain the tracking elements within the field-of-view of the localizer. For example, in some navigation systems, during initial setup of the navigation system, a display graphically represents a field-of-view of the localizer to guide initial placement of the tracking devices so that the tracking elements are located in the field-of-view free from obstructions to the line-of-sight. However, such navigation systems are unable to prevent obstructions to the line-of-sight that may arise during the surgical procedure as a result of the movement of objects into the line-of-sight, e.g., after the initial setup and during treatment of a patient, or to prevent the tracking elements from moving outside of the field-of-view.
When the line-of-sight is obstructed, or when the tracking elements are outside the field-of-view, tracking signals being transmitted from the tracking elements are not received by the localizer. As a result, errors can occur. Typically, in this situation, navigation is discontinued and error messages are conveyed to the user until the tracking signals are again received or the navigation system is reset. This can cause delays in surgical procedures. For instance, manipulators that rely on navigation data to autonomously position a cutting tool relative to the patient's tissue must cease operation should these errors occur. This could significantly increase the surgical procedure time, particularly if difficulty arises in restoring the line-of-sight. This is contrary to the demands of modern medical practice that require reduced surgery times in order to reduce risks of infection and risks associated with prolonged use of anesthesia.
Thus, there is a need in the art for navigation systems and methods that reduce tracking interruptions between tracking devices and a localizer receiving signals from the tracking devices so that surgical procedures are uninterrupted.